Hi Jurgen , yes there is a small problem with the Trumpeter /Hobby craft M1A1/M1A2 turrets . I'll use these pics to explain

Ok in this pic you see where the front left of the turret dosen't quite come down far enough (about 4mm short )


Now for the real thing , here you can see the proper dimensions of the front turret slope . I hope this ansers your question , glad to help .
The way that I fix this is to cut a new turret face out of plastic card and also a small wedge for the left side of the turret fill the underside gap with some putty and bace it with some plastic strips . I will take pics next time i fix one and post them . Toad out